The invention relates to a method of producing a part from cast and worked titanium alloy and intended for example for compressor discs for aircraft propulsion systems, and also to the parts obtained;
In their patent EP-B-0287486=U.S. Pat. No. 4,854,977=U.S. Pat. No. 4,878,966, the Applicants described a method of producing a part from titanium alloy having the following composition (% by mass): Al 3.8 to 5.4-Sn 1.5 to 2.5-Zr 2.8 to 4.8-Mo 1.5 to 4.5-Cr less than or equal to 2.5 and Cr+V=1.5 to 4.5-Fe&lt;2.0-Si&lt;0.3-O.sub.2 &lt;0.15 and Ti and impurities: the balance. According to this process, an ingot of the said alloy is hot worked this hot working comprising a roughing down under heat giving, giving a hot blank, then final working of at least a part of this blank preceded by preheating to a temperature situated above the real beta transus of the said hot rolled alloy, the ratio of this final rolling "S:s" (initial cross-section:final cross-section) preferably being greater than or equal to 2, after which the part blank obtained by this final working is subjected to a solution heat treatment and then an ageing treatment. The parts obtained have an ex-beta acicular structure with alpha pahse at grain boundaries. The best set of mechanical characteristics obtained thus (sample "FB", tests according to the direction L) is: Rm=1297 MPa- R.sub.p0.2 =1206 MPa-A%=6.9-K.sub.1c 51 MPa..sqroot.m. Creep at 400.degree. C. under 600 MPa: 0.2% in 48.5 hr and 0.5% in 384 hr.
In terms of service life, it has been found important to improve if possible the ductility (A%) without reducing the other mechanical characteristics.
The Applicants have sought to achieve this improvement and more generally to improve the compromise of mechanical properties obtained in such a titanium alloy component.